Doctors may one day be able to replace the use of potentially addictive opioid painkillers with the use of a form of light-based therapy, according to new findings from an American research group.
In the U.S. and many other countries, prescription opioid medications are commonly used to address serious pain in a range of treatment contexts. Unfortunately, all prescription opioids come with an inherent risk for the onset of opioid use disorder (a condition defined by opioid addiction and/or non-addicted opioid abuse). In a study published in April 2015 in the journal Neuron, researchers from two U.S. universities explored the possibility of developing a form of light-based therapy that mimics the effects of opioid medications while eliminating the risks for opioid abuse and opioid addiction.
How Do Opioids Work?
Whether consumed orally or injected or inhaled, all opioid substances reach the bloodstream and travel to the brain. After crossing the blood/brain barrier, these substances gain access to a group of receptors called opioid receptors, which sit on the surfaces of many of the brain’s nerve cells. After accessing the opioid receptors, prescription opioids and illicit/illegal opioid drugs have common effects that include disruption of the brain’s ability to sense pain or react to the body’s pain signals, a decrease in the rate of communication between the primary nerve cells in the central nervous system (spinal cord and brain) and a spike in activity in the brain’s pleasure center that triggers a highly rewarding sensation known as euphoria.
There are multiple types of opioid receptors in the human brain and elsewhere in the body. In addition to facilitating the effects of opioid substances, these receptors have functions that include helping to regulate the digestive system and assisting in the regulation of normal breathing. Specific types of opioid medications and drugs activate specific types of opioid receptors, and the impact of any opioid medication/drug partially depends on the type of receptor it activates.
Opioid Abuse and Addiction
Compared to everyday activities such as eating tasty food, having sex and participating in preferred leisure pursuits, opioid drugs and medications produce a much greater level of rewarding sensation inside the brain’s pleasure center. This means that the euphoria associated with opioid drug/medication use far outstrips the euphoria associated with non-substance-related pleasures. Unfortunately, some people purposefully misuse opioid medications or consume opioid drugs in repeated attempts to experience euphoric sensations. Others misuse opioid medications or drugs in a misguided attempt to relieve pain or treat other ailments. Whatever the underlying motivation, misuse of an opioid sets the stage for diagnosable opioid use disorder by producing ongoing alterations in the pleasure center and making the brain reliant on the continued excessive or inappropriate intake of opioids.
Potential for Light-Based Treatment
In the study published in Neuron, researchers from Washington University in Saint Louis and the University of Washington investigated the possibility of using light to trigger the brain’s opioid receptors and produce the painkilling effect normally produced by potentially addictive opioid medications. As part of this investigation, they used a test tube-based laboratory experiment to improve basic understanding of the ways in which opioid receptors work. During this experiment, the researchers combined a light-sensing protein found in the retina of the human eye with a specific form of opioid receptor known to play an important role in creating opioid medications’ pain-relieving qualities. They concluded that the protein-opioid receptor combination functioned in a manner similar to a switch and “turned on” the receptor’s ability to ease pain when light was present.
In a second experiment, the researchers injected light-sensing opioid receptors into the pleasure centers of a group of mice. They found that, when given the chance, the mice moved to light-rich areas in their environment that essentially triggered a spike in the level of rewarding sensation inside their brains. The researchers also found that they could vary the effects on the mice by controlling the color and intensity of the light the animals received.
Based on their findings, the study’s authors believe that it might be possible to develop new forms of light-based therapy specifically designed to produce the treatment benefits of opioid medications while drastically reducing or eliminating the chance for addiction-related brain changes or behaviors. Their findings also indicate that it might be possible to create a highly targeted form of light therapy that produces results tailored to the individual receiving treatment.